﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Interop;
using System.Reflection;
using System.ComponentModel;

namespace VolumeMaster {
	public class HotKey {


		/// <summary>
		/// The CallWndProc hook procedure is an application-defined or library-defined callback 
		/// function used with the SetWindowsHookEx function. The HOOKPROC type defines a pointer 
		/// to this callback function. CallWndProc is a placeholder for the application-defined 
		/// or library-defined function name.
		/// </summary>
		/// <param name="nCode">
		/// [in] Specifies whether the hook procedure must process the message. 
		/// If nCode is HC_ACTION, the hook procedure must process the message. 
		/// If nCode is less than zero, the hook procedure must pass the message to the 
		/// CallNextHookEx function without further processing and must return the 
		/// value returned by CallNextHookEx.
		/// </param>
		/// <param name="wParam">
		/// [in] Specifies whether the message was sent by the current thread. 
		/// If the message was sent by the current thread, it is nonzero; otherwise, it is zero. 
		/// </param>
		/// <param name="lParam">
		/// [in] Pointer to a CWPSTRUCT structure that contains details about the message. 
		/// </param>
		/// <returns>
		/// If nCode is less than zero, the hook procedure must return the value returned by CallNextHookEx. 
		/// If nCode is greater than or equal to zero, it is highly recommended that you call CallNextHookEx 
		/// and return the value it returns; otherwise, other applications that have installed WH_CALLWNDPROC 
		/// hooks will not receive hook notifications and may behave incorrectly as a result. If the hook 
		/// procedure does not call CallNextHookEx, the return value should be zero. 
		/// </returns>
		/// <remarks>
		/// http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/windowing/hooks/hookreference/hookfunctions/callwndproc.asp
		/// </remarks>
		private delegate int HookProc(int nCode, int wParam, IntPtr lParam);

		public static event EventHandler<MouseEventArgs> WheelMoved;
		public static event EventHandler<MouseEventArgs> MiddleDown;

		//##############################################################################
		#region Mouse hook processing

		/// <summary>
		/// This field is not objectively needed but we need to keep a reference on a delegate which will be 
		/// passed to unmanaged code. To avoid GC to clean it up.
		/// When passing delegates to unmanaged code, they must be kept alive by the managed application 
		/// until it is guaranteed that they will never be called.
		/// </summary>
		private static HookProc s_MouseDelegate;

		/// <summary>
		/// Stores the handle to the mouse hook procedure.
		/// </summary>
		private static int s_MouseHookHandle;

		/// <summary>
		/// A callback function which will be called every Time a mouse activity detected.
		/// </summary>
		/// <param name="nCode">
		/// [in] Specifies whether the hook procedure must process the message. 
		/// If nCode is HC_ACTION, the hook procedure must process the message. 
		/// If nCode is less than zero, the hook procedure must pass the message to the 
		/// CallNextHookEx function without further processing and must return the 
		/// value returned by CallNextHookEx.
		/// </param>
		/// <param name="wParam">
		/// [in] Specifies whether the message was sent by the current thread. 
		/// If the message was sent by the current thread, it is nonzero; otherwise, it is zero. 
		/// </param>
		/// <param name="lParam">
		/// [in] Pointer to a CWPSTRUCT structure that contains details about the message. 
		/// </param>
		/// <returns>
		/// If nCode is less than zero, the hook procedure must return the value returned by CallNextHookEx. 
		/// If nCode is greater than or equal to zero, it is highly recommended that you call CallNextHookEx 
		/// and return the value it returns; otherwise, other applications that have installed WH_CALLWNDPROC 
		/// hooks will not receive hook notifications and may behave incorrectly as a result. If the hook 
		/// procedure does not call CallNextHookEx, the return value should be zero. 
		/// </returns>
		private static int MouseHookProc(int nCode, int wParam, IntPtr lParam) {
			if (nCode >= 0) {
				//Marshall the data from callback.
				MouseLLHookStruct mouseHookStruct = (MouseLLHookStruct)Marshal.PtrToStructure(lParam, typeof(MouseLLHookStruct));

				//detect button clicked
				MouseButtons button = MouseButtons.None;
				short mouseDelta = 0;
				int clickCount = 0;
				bool mouseDown = false;
				bool mouseUp = false;

				switch (wParam) {
					case WM_LBUTTONDOWN:
						mouseDown = true;
						button = MouseButtons.Left;
						clickCount = 1;
						break;
					case WM_LBUTTONUP:
						mouseUp = true;
						button = MouseButtons.Left;
						clickCount = 1;
						break;
					case WM_LBUTTONDBLCLK:
						button = MouseButtons.Left;
						clickCount = 2;
						break;
					case WM_RBUTTONDOWN:
						mouseDown = true;
						button = MouseButtons.Right;
						clickCount = 1;
						break;
					case WM_RBUTTONUP:
						mouseUp = true;
						button = MouseButtons.Right;
						clickCount = 1;
						break;
					case WM_RBUTTONDBLCLK:
						button = MouseButtons.Right;
						clickCount = 2;
						break;
					case WM_MBUTTONDOWN:
						button = MouseButtons.Middle;
						mouseDown = true;
						clickCount = 1;
						break;
					case WM_MBUTTONUP:
						button = MouseButtons.Middle;
						clickCount = 1;
						break;
					case WM_MOUSEWHEEL:
						//If the message is WM_MOUSEWHEEL, the high-order word of MouseData member is the wheel delta. 
						//One wheel click is defined as WHEEL_DELTA, which is 120. 
						//(value >> 16) & 0xffff; retrieves the high-order word from the given 32-bit value
						mouseDelta = (short)((mouseHookStruct.MouseData >> 16) & 0xffff);

						//TODO: X BUTTONS (I havent them so was unable to test)
						//If the message is WM_XBUTTONDOWN, WM_XBUTTONUP, WM_XBUTTONDBLCLK, WM_NCXBUTTONDOWN, WM_NCXBUTTONUP, 
						//or WM_NCXBUTTONDBLCLK, the high-order word specifies which X button was pressed or released, 
						//and the low-order word is reserved. This value can be one or more of the following values. 
						//Otherwise, MouseData is not used. 
						break;
				}

				if (mouseDelta != 0 && ShiftButtonDown && WheelMoved != null) {
						WheelMoved(null, 
							new MouseEventArgs(
								button,
								clickCount,
								mouseHookStruct.Point.X,
								mouseHookStruct.Point.Y,
								mouseDelta));
										
					//-- Swallow this Hook
					return -1;
				} else if (
					button == MouseButtons.Middle && mouseDown &&
					ShiftButtonDown && (MiddleDown != null)) {
					MiddleDown(null,
						new MouseEventArgs(
							button,
							clickCount,
							mouseHookStruct.Point.X,
							mouseHookStruct.Point.Y,
							mouseDelta));
					return -1;
				}
			}

			//call next hook
			return CallNextHookEx(s_MouseHookHandle, nCode, wParam, lParam);
		}

		static bool ShiftButtonDown {
			get {
				return
					(0 != (GetAsyncKeyState(VK_SHIFT) & 0x8000)); 
			}
		}

		[DllImport("user32.dll")]
		static extern short GetAsyncKeyState(int vKey);

		public static void EnsureSubscribedToGlobalMouseEvents() {
			// install Mouse hook only if it is not installed and must be installed
			if (s_MouseHookHandle == 0) {
				//See comment of this field. To avoid GC to clean it up.
				s_MouseDelegate = MouseHookProc;
				//install hook
				s_MouseHookHandle = SetWindowsHookEx(
						WH_MOUSE_LL,
						s_MouseDelegate,
						IntPtr.Zero,
						0);
				//If SetWindowsHookEx fails.
				if (s_MouseHookHandle == 0) {
					//Returns the error code returned by the last unmanaged function called using platform invoke that has the DllImportAttribute.SetLastError flag set. 
					int errorCode = Marshal.GetLastWin32Error();
					//do cleanup

					//Initializes and throws a new instance of the Win32Exception class with the specified error. 
					throw new Win32Exception(errorCode);
				}
			}
		}

		private static void TryUnsubscribeFromGlobalMouseEvents() {
			//if no subsribers are registered unsubsribe from hook
			
				ForceUnsunscribeFromGlobalMouseEvents();
			
		}

		private static void ForceUnsunscribeFromGlobalMouseEvents() {
			if (s_MouseHookHandle != 0) {
				//uninstall hook
				int result = UnhookWindowsHookEx(s_MouseHookHandle);
				//reset invalid handle
				s_MouseHookHandle = 0;
				//Free up for GC
				s_MouseDelegate = null;
				//if failed and exception must be thrown
				if (result == 0) {
					//Returns the error code returned by the last unmanaged function called using platform invoke that has the DllImportAttribute.SetLastError flag set. 
					int errorCode = Marshal.GetLastWin32Error();
					//Initializes and throws a new instance of the Win32Exception class with the specified error. 
					throw new Win32Exception(errorCode);
				}
			}
		}

		/// <summary>
		/// The Point structure defines the X- and Y- coordinates of a point. 
		/// </summary>
		/// <remarks>
		/// http://msdn.microsoft.com/library/default.asp?url=/library/en-us/gdi/rectangl_0tiq.asp
		/// </remarks>
		[StructLayout(LayoutKind.Sequential)]
		public struct Point {
			/// <summary>
			/// Specifies the X-coordinate of the point. 
			/// </summary>
			public int X;
			/// <summary>
			/// Specifies the Y-coordinate of the point. 
			/// </summary>
			public int Y;
		}

		/// <summary>
		/// The MSLLHOOKSTRUCT structure contains information about a low-level keyboard input event. 
		/// </summary>
		[StructLayout(LayoutKind.Sequential)]
		private struct MouseLLHookStruct {
			/// <summary>
			/// Specifies a Point structure that contains the X- and Y-coordinates of the cursor, in screen coordinates. 
			/// </summary>
			public Point Point;
			/// <summary>
			/// If the message is WM_MOUSEWHEEL, the high-order word of this member is the wheel delta. 
			/// The low-order word is reserved. A positive value indicates that the wheel was rotated forward, 
			/// away from the user; a negative value indicates that the wheel was rotated backward, toward the user. 
			/// One wheel click is defined as WHEEL_DELTA, which is 120. 
			///If the message is WM_XBUTTONDOWN, WM_XBUTTONUP, WM_XBUTTONDBLCLK, WM_NCXBUTTONDOWN, WM_NCXBUTTONUP,
			/// or WM_NCXBUTTONDBLCLK, the high-order word specifies which X button was pressed or released, 
			/// and the low-order word is reserved. This value can be one or more of the following values. Otherwise, MouseData is not used. 
			///XBUTTON1
			///The first X button was pressed or released.
			///XBUTTON2
			///The second X button was pressed or released.
			/// </summary>
			public int MouseData;
			/// <summary>
			/// Specifies the event-injected flag. An application can use the following value to test the mouse Flags. Value Purpose 
			///LLMHF_INJECTED Test the event-injected flag.  
			///0
			///Specifies whether the event was injected. The value is 1 if the event was injected; otherwise, it is 0.
			///1-15
			///Reserved.
			/// </summary>
			public int Flags;
			/// <summary>
			/// Specifies the Time stamp for this message.
			/// </summary>
			public int Time;
			/// <summary>
			/// Specifies extra information associated with the message. 
			/// </summary>
			public int ExtraInfo;
		}

		// Summary:
		//     Specifies constants that define which mouse button was pressed.
		[Flags]
		[ComVisible(true)]
		public enum MouseButtons {
			// Summary:
			//     No mouse button was pressed.
			None = 0,
			//
			// Summary:
			//     The left mouse button was pressed.
			Left = 1048576,
			//
			// Summary:
			//     The right mouse button was pressed.
			Right = 2097152,
			//
			// Summary:
			//     The middle mouse button was pressed.
			Middle = 4194304,
			//
			// Summary:
			//     The first XButton was pressed.
			XButton1 = 8388608,
			//
			// Summary:
			//     The second XButton was pressed.
			XButton2 = 16777216,
		}


		// Summary:
		//     Provides data for the System.Windows.Forms.Control.MouseUp, System.Windows.Forms.Control.MouseDown,
		//     and System.Windows.Forms.Control.MouseMove events.
		[ComVisible(true)]
		public class MouseEventArgs : HandledEventArgs {
			// Summary:
			//     Initializes a new instance of the System.Windows.Forms.MouseEventArgs class.
			//
			// Parameters:
			//   button:
			//     One of the System.Windows.Forms.MouseButtons values indicating which mouse
			//     button was pressed.
			//
			//   clicks:
			//     The number of times a mouse button was pressed.
			//
			//   x:
			//     The x-coordinate of a mouse click, in pixels.
			//
			//   y:
			//
			//   delta:
			//     A signed count of the number of detents the wheel has rotated.
			public MouseEventArgs(MouseButtons button, int clicks, int x, int y, int delta) {
				Button = button;
				Clicks = clicks;
				X = x;
				Y = y;
				Delta = delta;
			}

			// Summary:
			//     Gets which mouse button was pressed.
			//
			// Returns:
			//     One of the System.Windows.Forms.MouseButtons values.
			public MouseButtons Button { get; set; }
			//
			// Summary:
			//     Gets the number of times the mouse button was pressed and released.
			//
			// Returns:
			//     An System.Int32 containing the number of times the mouse button was pressed
			//     and released.
			public int Clicks { get; set; }
			//
			// Summary:
			//     Gets a signed count of the number of detents the mouse wheel has rotated.
			//     A detent is one notch of the mouse wheel.
			//
			// Returns:
			//     A signed count of the number of detents the mouse wheel has rotated.
			public int Delta { get; set; }
			//
			// Summary:
			//     Gets the location of the mouse during the generating mouse event.
			//
			// Returns:
			//     A System.Drawing.Point containing the x- and y- coordinate of the mouse,
			//     in pixels.
			public Point Location { get; set; }
			//
			// Summary:
			//     Gets the x-coordinate of the mouse during the generating mouse event.
			//
			// Returns:
			//     The x-coordinate of the mouse, in pixels.
			public int X { get; set; }
			//
			// Summary:
			//     Gets the y-coordinate of the mouse during the generating mouse event.
			//
			// Returns:
			//     The y-coordinate of the mouse, in pixels.
			public int Y { get; set; }
		}

		#endregion


		#region Windows constants

		//values from Winuser.h in Microsoft SDK.
		/// <summary>
		/// Windows NT/2000/XP: Installs a hook procedure that monitors low-level mouse input events.
		/// </summary>
		private const int WH_MOUSE_LL = 14;

		/// <summary>
		/// Windows NT/2000/XP: Installs a hook procedure that monitors low-level keyboard  input events.
		/// </summary>
		private const int WH_KEYBOARD_LL = 13;

		/// <summary>
		/// Installs a hook procedure that monitors mouse messages. For more information, see the MouseProc hook procedure. 
		/// </summary>
		private const int WH_MOUSE = 7;

		/// <summary>
		/// Installs a hook procedure that monitors keystroke messages. For more information, see the KeyboardProc hook procedure. 
		/// </summary>
		private const int WH_KEYBOARD = 2;

		/// <summary>
		/// The WM_MOUSEMOVE message is posted to a window when the cursor moves. 
		/// </summary>
		private const int WM_MOUSEMOVE = 0x200;

		/// <summary>
		/// The WM_LBUTTONDOWN message is posted when the user presses the left mouse button 
		/// </summary>
		private const int WM_LBUTTONDOWN = 0x201;

		/// <summary>
		/// The WM_RBUTTONDOWN message is posted when the user presses the right mouse button
		/// </summary>
		private const int WM_RBUTTONDOWN = 0x204;

		/// <summary>
		/// The WM_MBUTTONDOWN message is posted when the user presses the middle mouse button 
		/// </summary>
		private const int WM_MBUTTONDOWN = 0x207;

		/// <summary>
		/// The WM_LBUTTONUP message is posted when the user releases the left mouse button 
		/// </summary>
		private const int WM_LBUTTONUP = 0x202;

		/// <summary>
		/// The WM_RBUTTONUP message is posted when the user releases the right mouse button 
		/// </summary>
		private const int WM_RBUTTONUP = 0x205;

		/// <summary>
		/// The WM_MBUTTONUP message is posted when the user releases the middle mouse button 
		/// </summary>
		private const int WM_MBUTTONUP = 0x208;

		/// <summary>
		/// The WM_LBUTTONDBLCLK message is posted when the user double-clicks the left mouse button 
		/// </summary>
		private const int WM_LBUTTONDBLCLK = 0x203;

		/// <summary>
		/// The WM_RBUTTONDBLCLK message is posted when the user double-clicks the right mouse button 
		/// </summary>
		private const int WM_RBUTTONDBLCLK = 0x206;

		/// <summary>
		/// The WM_RBUTTONDOWN message is posted when the user presses the right mouse button 
		/// </summary>
		private const int WM_MBUTTONDBLCLK = 0x209;

		/// <summary>
		/// The WM_MOUSEWHEEL message is posted when the user presses the mouse wheel. 
		/// </summary>
		private const int WM_MOUSEWHEEL = 0x020A;

		/// <summary>
		/// The WM_KEYDOWN message is posted to the window with the keyboard focus when a nonsystem 
		/// key is pressed. A nonsystem key is a key that is pressed when the ALT key is not pressed.
		/// </summary>
		private const int WM_KEYDOWN = 0x100;

		/// <summary>
		/// The WM_KEYUP message is posted to the window with the keyboard focus when a nonsystem 
		/// key is released. A nonsystem key is a key that is pressed when the ALT key is not pressed, 
		/// or a keyboard key that is pressed when a window has the keyboard focus.
		/// </summary>
		private const int WM_KEYUP = 0x101;

		/// <summary>
		/// The WM_SYSKEYDOWN message is posted to the window with the keyboard focus when the user 
		/// presses the F10 key (which activates the menu bar) or holds down the ALT key and then 
		/// presses another key. It also occurs when no window currently has the keyboard focus; 
		/// in this case, the WM_SYSKEYDOWN message is sent to the active window. The window that 
		/// receives the message can distinguish between these two contexts by checking the context 
		/// code in the lParam parameter. 
		/// </summary>
		private const int WM_SYSKEYDOWN = 0x104;

		/// <summary>
		/// The WM_SYSKEYUP message is posted to the window with the keyboard focus when the user 
		/// releases a key that was pressed while the ALT key was held down. It also occurs when no 
		/// window currently has the keyboard focus; in this case, the WM_SYSKEYUP message is sent 
		/// to the active window. The window that receives the message can distinguish between 
		/// these two contexts by checking the context code in the lParam parameter. 
		/// </summary>
		private const int WM_SYSKEYUP = 0x105;

		private const byte VK_SHIFT = 0x10;
		private const byte VK_CAPITAL = 0x14;
		private const byte VK_NUMLOCK = 0x90;

		#endregion

		#region Windows function imports

		/// <summary>
		/// The CallNextHookEx function passes the hook information to the next hook procedure in the current hook chain. 
		/// A hook procedure can call this function either before or after processing the hook information. 
		/// </summary>
		/// <param name="idHook">Ignored.</param>
		/// <param name="nCode">
		/// [in] Specifies the hook code passed to the current hook procedure. 
		/// The next hook procedure uses this code to determine how to process the hook information.
		/// </param>
		/// <param name="wParam">
		/// [in] Specifies the wParam value passed to the current hook procedure. 
		/// The meaning of this parameter depends on the type of hook associated with the current hook chain. 
		/// </param>
		/// <param name="lParam">
		/// [in] Specifies the lParam value passed to the current hook procedure. 
		/// The meaning of this parameter depends on the type of hook associated with the current hook chain. 
		/// </param>
		/// <returns>
		/// This value is returned by the next hook procedure in the chain. 
		/// The current hook procedure must also return this value. The meaning of the return value depends on the hook type. 
		/// For more information, see the descriptions of the individual hook procedures.
		/// </returns>
		/// <remarks>
		/// http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/windowing/hooks/hookreference/hookfunctions/setwindowshookex.asp
		/// </remarks>
		[DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
		private static extern int CallNextHookEx(
				int idHook,
				int nCode,
				int wParam,
				IntPtr lParam);


		/// <summary>
		/// The SetWindowsHookEx function installs an application-defined hook procedure into a hook chain. 
		/// You would install a hook procedure to monitor the system for certain types of events. These events 
		/// are associated either with a specific thread or with all threads in the same desktop as the calling thread. 
		/// </summary>
		/// <param name="idHook">
		/// [in] Specifies the type of hook procedure to be installed. This parameter can be one of the following values.
		/// </param>
		/// <param name="lpfn">
		/// [in] Pointer to the hook procedure. If the dwThreadId parameter is zero or specifies the identifier of a 
		/// thread created by a different process, the lpfn parameter must point to a hook procedure in a dynamic-link 
		/// library (DLL). Otherwise, lpfn can point to a hook procedure in the code associated with the current process.
		/// </param>
		/// <param name="hMod">
		/// [in] Handle to the DLL containing the hook procedure pointed to by the lpfn parameter. 
		/// The hMod parameter must be set to NULL if the dwThreadId parameter specifies a thread created by 
		/// the current process and if the hook procedure is within the code associated with the current process. 
		/// </param>
		/// <param name="dwThreadId">
		/// [in] Specifies the identifier of the thread with which the hook procedure is to be associated. 
		/// If this parameter is zero, the hook procedure is associated with all existing threads running in the 
		/// same desktop as the calling thread. 
		/// </param>
		/// <returns>
		/// If the function succeeds, the return value is the handle to the hook procedure.
		/// If the function fails, the return value is NULL. To get extended error information, call GetLastError.
		/// </returns>
		/// <remarks>
		/// http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/windowing/hooks/hookreference/hookfunctions/setwindowshookex.asp
		/// </remarks>
		[DllImport("user32.dll", CharSet = CharSet.Auto,
				CallingConvention = CallingConvention.StdCall, SetLastError = true)]
		private static extern int SetWindowsHookEx(
				int idHook,
				HookProc lpfn,
				IntPtr hMod,
				int dwThreadId);

		/// <summary>
		/// The UnhookWindowsHookEx function removes a hook procedure installed in a hook chain by the SetWindowsHookEx function. 
		/// </summary>
		/// <param name="idHook">
		/// [in] Handle to the hook to be removed. This parameter is a hook handle obtained by a previous call to SetWindowsHookEx. 
		/// </param>
		/// <returns>
		/// If the function succeeds, the return value is nonzero.
		/// If the function fails, the return value is zero. To get extended error information, call GetLastError.
		/// </returns>
		/// <remarks>
		/// http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/windowing/hooks/hookreference/hookfunctions/setwindowshookex.asp
		/// </remarks>
		[DllImport("user32.dll", CharSet = CharSet.Auto,
				CallingConvention = CallingConvention.StdCall, SetLastError = true)]
		private static extern int UnhookWindowsHookEx(int idHook);

		/// <summary>
		/// The GetDoubleClickTime function retrieves the current double-click time for the mouse. A double-click is a series of two clicks of the 
		/// mouse button, the second occurring within a specified time after the first. The double-click time is the maximum number of 
		/// milliseconds that may occur between the first and second click of a double-click. 
		/// </summary>
		/// <returns>
		/// The return value specifies the current double-click time, in milliseconds. 
		/// </returns>
		/// <remarks>
		/// http://msdn.microsoft.com/en-us/library/ms646258(VS.85).aspx
		/// </remarks>
		[DllImport("user32")]
		public static extern int GetDoubleClickTime();

		/// <summary>
		/// The ToAscii function translates the specified virtual-key code and keyboard 
		/// state to the corresponding character or characters. The function translates the code 
		/// using the input language and physical keyboard layout identified by the keyboard layout handle.
		/// </summary>
		/// <param name="uVirtKey">
		/// [in] Specifies the virtual-key code to be translated. 
		/// </param>
		/// <param name="uScanCode">
		/// [in] Specifies the hardware scan code of the key to be translated. 
		/// The high-order bit of this value is set if the key is up (not pressed). 
		/// </param>
		/// <param name="lpbKeyState">
		/// [in] Pointer to a 256-byte array that contains the current keyboard state. 
		/// Each element (byte) in the array contains the state of one key. 
		/// If the high-order bit of a byte is set, the key is down (pressed). 
		/// The low bit, if set, indicates that the key is toggled on. In this function, 
		/// only the toggle bit of the CAPS LOCK key is relevant. The toggle state 
		/// of the NUM LOCK and SCROLL LOCK keys is ignored.
		/// </param>
		/// <param name="lpwTransKey">
		/// [out] Pointer to the buffer that receives the translated character or characters. 
		/// </param>
		/// <param name="fuState">
		/// [in] Specifies whether a menu is active. This parameter must be 1 if a menu is active, or 0 otherwise. 
		/// </param>
		/// <returns>
		/// If the specified key is a dead key, the return value is negative. Otherwise, it is one of the following values. 
		/// Value Meaning 
		/// 0 The specified virtual key has no translation for the current state of the keyboard. 
		/// 1 One character was copied to the buffer. 
		/// 2 Two characters were copied to the buffer. This usually happens when a dead-key character 
		/// (accent or diacritic) stored in the keyboard layout cannot be composed with the specified 
		/// virtual key to form a single character. 
		/// </returns>
		/// <remarks>
		/// http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/userinput/keyboardinput/keyboardinputreference/keyboardinputfunctions/toascii.asp
		/// </remarks>
		[DllImport("user32")]
		private static extern int ToAscii(
				int uVirtKey,
				int uScanCode,
				byte[] lpbKeyState,
				byte[] lpwTransKey,
				int fuState);

		/// <summary>
		/// The GetKeyboardState function copies the status of the 256 virtual keys to the 
		/// specified buffer. 
		/// </summary>
		/// <param name="pbKeyState">
		/// [in] Pointer to a 256-byte array that contains keyboard key states. 
		/// </param>
		/// <returns>
		/// If the function succeeds, the return value is nonzero.
		/// If the function fails, the return value is zero. To get extended error information, call GetLastError. 
		/// </returns>
		/// <remarks>
		/// http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/userinput/keyboardinput/keyboardinputreference/keyboardinputfunctions/toascii.asp
		/// </remarks>
		[DllImport("user32")]
		private static extern int GetKeyboardState(byte[] pbKeyState);

		/// <summary>
		/// The GetKeyState function retrieves the status of the specified virtual key. The status specifies whether the key is up, down, or toggled 
		/// (on, off—alternating each time the key is pressed). 
		/// </summary>
		/// <param name="vKey">
		/// [in] Specifies a virtual key. If the desired virtual key is a letter or digit (A through Z, a through z, or 0 through 9), nVirtKey must be set to the ASCII value of that character. For other keys, it must be a virtual-key code. 
		/// </param>
		/// <returns>
		/// The return value specifies the status of the specified virtual key, as follows: 
		///If the high-order bit is 1, the key is down; otherwise, it is up.
		///If the low-order bit is 1, the key is toggled. A key, such as the CAPS LOCK key, is toggled if it is turned on. The key is off and untoggled if the low-order bit is 0. A toggle key's indicator light (if any) on the keyboard will be on when the key is toggled, and off when the key is untoggled.
		/// </returns>
		/// <remarks>http://msdn.microsoft.com/en-us/library/ms646301.aspx</remarks>
		[DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
		private static extern short GetKeyState(int vKey);

		#endregion

	}
}
